Chemistry: Principles and reactions

Matter: anything that has mass and occupies space. Matter exists in three phases: SolidLiquidGas

Mixtures are combinations of two or more pure substances. Pure substances have a fixed composition and unique set of properties Pure substances are either elements (aluminum, copper, carbon) or compounds (carbon tetrachloride, ammonium)

An element is a type of matter that can’t be broken down into more than one substance. Copper makes wires, carbon makes charcoal, aluminum makes forms and spoons and foil. Elements are identified on the periodic table by their symbol, which is one or two letters.

A compound is a pure substance that contains more than one element. Water is the most obvious one you encounter—oxygen and hydrogen Compounds have fixed compositions. Water is always 2 hydrogen atoms attached to one oxygen atom (H2O), it always has a mass of about 18 g/mol, of which 16 g are always the oxygen and 2 g are the hydrogen Any other combination ain’t water.

Mixtures are combinations of two or more substances that don’t react chemically. If you mix iron shavings and sand, they don’t react. The iron is still iron and the sand is still sand. On the other hand, if you mix sodium and chlorine, they react to form table salt. Mixtures can be divided into two types: homogeneous and heterogeneous.

Homogeneous mixtures appear to have the same composition throughout. Translation—it looks like one thing. Brass is actually a copper / zinc mix The ocean is saltwater. Kool-aid is sugar water. Also known as solutions.

Heterogeneous mixtures are nonuniform. In other words, they look like a bunch of stuff mixed together. Granite is a mixture of several different minerals Oil and water don’t mix.

Science measures. That’s all it’s good for. Everything it knows, everything it tells you, comes from some person measuring something. A measurement always consists of two things: A) a number, like 7, or 97, or 1.2 x B) a unit, like inches, or hertz, or cm, or degrees C, or (L)(atm)(mol -1 )(K -1 )

The rest of the universe uses the metric system. That means you have to learn it. The metric system is based on the idea that the unit tells us what type of measurement Meter = length, gram = mass, liter = volume The prefix to the unit tells us how big the number is : Centi = 1/100, milli = 1/1000, kilo = There are more prefixes—if you come across an unfamiliar one, look it up. NOTE: 1 mL = 1 cc (cubic centimeter)

Technically, no. Mass is the amount of matter in a object. Weight is the measure of the gravitational force acting on the object. If you went to the moon, your mass wouldn’t change, but your weight would. But, since we’re not going to the moon, we use the words to mean the same thing in this class.

Three units: F, C, or Kelvin tF = 1.8 tC + 32 tC = (tF – 32) / 1.8 tK = tC tC = tK Know these.

Every measurement is uncertain. How tall are you? How many decimal points do you carry your measurement out to? If you convey information, you are obligated to also tell people how sure you are. We do this with decimal points. 8 mL ( mL) 8.0 mL ( mL) 8.00 mL ( mL)

All non-zeroes are significant: mL All zeroes between non-zeroes are significant: g Zeroes to the right of the decimal point are significant: 5.20 cm Zeroes acting as placeholders are NOT significant: kg, 600 miles

Any number can be expressed as a factor of 10. For example, 1000 is the same as 1 x 10 3 The exponent tells us where to move the decimal point. Positive exponents are larger than 1 Negative exponents are smaller than 1 In the example above, the exponent needs to move 3 positive places. 1  1000 (Had it been a -3, the number would have been.001)

The answer you develop cannot have more significant digits than the numbers you worked with = 3.8 (not 3.75) 1.5 x = 4.5 (not ) See appendix 3 for help on this subject.

If you have 16 wheels, how many bikes can you make? If you have 3600 mL, how many liters is that? Table 1.3 is helpful, as is Example wheels1 bikeAnswer: 8 bikes 2 wheels 3600 mL1 LAnswer: 3.6 L 1000 mL

Convert 564, 462, 235 cm to km Convert 92 inches to meters (HINT: 1 inch is equivalent to 2.54 centimeters) Convert 62 miles per hour to inches per day. Answer: km Answer: 2.3 m Answer: 9.4 x 10 7 inches / day

Identify the information you have, and separate what’s important from what’s not. Decide what to do before you start working. USE DIMENSIONAL ANALYSIS and WRITE DOWN ALL UNITS. Use common sense to determine if your answer is logical. If you convert 62 miles per hour into 16 inches per day, bells should ring inside your skull! Pay attention to details--significant digits and scientific notation in your answer.

The properties of a substance are the things that distinguish it from all other substances Chemical properties are observed when a substance reacts (or fails to): Helium is a nonreactive gas, so if it reacts, it’s not helium. Iron rusts in water…carbon combusts… Physical changes can be observed without changing the substance: melting and boiling points help us identify things

Density = mass per volume (usually g / mL). One mL of copper always has a mass of 8.94 g. If 18 g of an unknown chemical have a volume of 9 mL, is it copper? What volume would 18 g of copper occupy? Solubility= how much of a solid can be dissolved in a fixed amount of liquid. Table sugar has a solubility of 487 g sugar / 100 g water (at 100°C). How much sugar could be dissolved in 250 g of boiling water?

Summary problem c-f